Fusion of spinal vertebrae is often necessary to relieve debilitating pain or to correct a deformity. Cervical spinal fusion is often prescribed for patients suffering from degenerative disk disease whose symptoms may include neck pain of discogenic origin with degeneration of the disk confirmed by patient history and radiographic studies, trauma including fractures, tumors, deformity such as kyphosis, lordosis or scoliosis, pseudoarthrosis, or failed previous fusions.
Spinal surgical fusion is the process of bringing together two or more vertebrae under conditions whereby the vertebrae fuse together to form a unitary member of the spinal column. When vertebrae are fused, e.g., with bone grafts, graft extenders, or interbody spacers such as interbody cages or boxes (collectively termed “grafts” herein), it is desirable to stabilize the fused vertebrae using an apparatus such as a plate to fixate one cervical vertebra to another to promote fusion across motion segments. In carrying out the procedure, the members must be brought together under conditions that are critically controlled to prevent infection, maintain alignment of opposing members, and allow for the stress in the bone that is generated as the healing process matures. Immobilization is an important requirement during this healing process.
Another common spinal ailment is the degeneration of an intervertebral disc caused by trauma, disease, and/or aging. A degenerated intervertebral disc may have to be partially or fully removed from a spinal column. Partial or full removal of an intervertebral disc may destabilize a spinal column. Destabilization of a spinal column may alter the natural separation distance between adjacent vertebrae. Maintaining a natural separation distance between vertebrae may help prevent pressure from being applied to nerves that pass between vertebral bodies. Excessive pressure applied to the nerves may cause pain and/or nerve damage. During a spinal fixation procedure, a spinal implant may be inserted in a space created by removal or partial removal of an intervertebral disc between adjacent vertebrae. A spinal implant may maintain the height of the spine and restore stability to the spine. Intervertebral bone growth may fuse the implant to adjacent vertebrae.
A spinal implant may be inserted during a spinal fixation procedure using an anterior, lateral, or posterior spinal approach. A discectomy may be performed to remove or partially remove a defective and/or damaged intervertebral disc. A discectomy creates a disc space for a spinal implant. After a discectomy, a spinal implant may be inserted into the disc space. One or more spinal implants may be inserted between a pair of vertebrae. Spinal implants may be inserted into disc spaces prepared between more than one pair of vertebrae during a spinal fusion procedure.
A spinal plate may be coupled to vertebrae after insertion of one or more spinal implants. A spinal plate may stabilize the vertebrae and inhibit back out of the spinal implant from between vertebrae. A spinal plate may share a compressive load applied to one or, more spinal implants inserted between vertebrae. Fasteners, such as bone screws, may couple the spinal plate to vertebrae. Spinal plates may stabilize sections of cervical spine and/or sections of lumbar, spine.
The process of bone healing has been widely studied. Micro-fractures, once thought to be negative events, are now seen as part of the natural process of bone remodeling and occur within bone in the course of everyday wear and tear. In the early stage of these cycles, bone resorption is first accomplished by osteoclasts. This is followed by new bone formation by osteoblasts over the latter part of each cycle. Osteoblasts serve a critical role in new bone formation, filling in the bony cavity in areas of bone remodeling with bone matrix. Osteoblasts are further known to release cytokines to attract osteoclasts. Osteoclasts serve to release proteases, which act to dissolve bone mineral matrix, collagen, and clear away damaged bone. Osetoclasts also releases matrix-bound growth factors and may serve as a chemo attractant for osteoblasts. The process of bone healing is currently believed to be a continual cycle, in which the body's response to microfractures and stress injuries within healing bone actually serve to strengthen healing ultimately and produce more solid bone.
What is needed are systems, methods and devices such as a plating system to repair bone fractures or to stabilize separate bony structures and allow them to fuse into a single item that may incorporate or harness the elements of the natural bone healing process. What are needed are systems, methods and devices that promote optimal fusion at a graft, particularly at cervical vertebrae. Further, methods, systems and devices that utilize a minimum number of parts and which may be easily customized intraoperatively by the surgeon are also needed.